The present invention relates to a machine for sealing plastic profiled elements, particularly PVC.
In background art, profiled elements in plastic like PVC or the like, mostly used as window frames, are sealed to each other by the melting of respective head surfaces in order to achieve a frame structure applicable to doors, windows, or to the wall frames of same.
In particular, melting occurs by heating the portions to be connected by means of suitable plates with electrical heating elements and then pressing the heated portions one against the other to facilitate their melting.
Generally, the heated portions are the head ending parts of the profiled elements, suitably cut at 45° to define, e.g., a right-angled portion of a respective frame.
This methodology is implemented by sealing machines having respective retention members of the profiled elements, movable in mutual approach to bring into contact the heated ending parts to be sealed.
Other machines are also equipped with finishing systems, adapted to remove the sealing bead which is formed during the melting of the two profiled elements.
In fact, at the line of union of the two profiled elements (surfaces cut at 45°), the portion of excess molten material flows out and forms a bead projecting from the visible surface of the profiled elements.
For this reason, in order to give the finished frame an appreciable aesthetic appearance, the profiled elements, once sealed, undergo a bead removal operation.
The known sealing devices briefly described above do however have major drawbacks, mainly related to the formation of the aforementioned sealing bead.
In fact, it must be considered that the sealing area of the plastic profiled elements is not completely homogeneous and therefore, to make the profiles regular, a lot of material is melted with the consequent formation of an abundant bead, and therefore a lot of reject material which must be removed. Furthermore, the finishing processes adapted to remove the bead and clean the sealing area, significantly affect the overall frame machining time.
It should be realized, in fact, that for each frame seal, the profiled elements have to be subsequently machined.
Furthermore, for the spoke profiled elements, the removal of said bead is highly complicated.
To this must be added that the machinery used for the above mentioned finishing operations is cumbersome, complex and particularly expensive.
This entails the need to sustain additional costs and machining times, including because of the presence of further cumbersome equipment and tools.
The patent document WO 2013/132406 A1 shows a method and a device which allow overcoming the above drawbacks.
The system shown in WO 2013/132406 A1, in fact, has two mobile retention members onto which are mounted the profiled elements and allows sealing them without forming any sealing bead, thanks to a prior milling operation of the areas to seal, adapted to obtain on the profiled elements a containment compartment for the sealing bead, and the application of containment pressers, which are juxtaposed with profiled elements heated during sealing and prevent the molten material from coming out of the containment compartment.
An improved type of pressing element is shown in the patent document WO 2014/122572 A1.
The methods and devices shown in the documents WO 2013/132406 A1 and WO 2014/122572 A1 are also susceptible to further improvements aimed at obtaining frames for doors and windows of even higher quality.
In this respect the fact is underlined that the containment pressers provided in documents WO 2013/132406 A1 and WO 2014/122572 A1 allow containing the sealing bead only at the main faces of the profiled elements but not at the lateral faces, i.e., those designed to define the perimeter sides of the door/window that couple with the relative wall frame (the outer perimeter side) and with the inner panel in glass or other material (the inner perimeter side).
In this sense, the presence of a sealing bead on the outer perimeter side can be unsightly and/or dangerous (sometimes the sealing bead has a sharp profile) when the door/window is open.
To obviate at least in part to these drawbacks, the devices built according to the teachings of the documents WO 2013/132406 A1 and WO 2014/122572 A1 have been provided with suitable lateral containment systems consisting of two mobile edges, made of aluminum and mounted on the retention members, one edge for each retention member.
When the heated profiled elements are brought nearer to each other to melt the areas to seal, the edges settle on the profiled elements (one edge for each profiled element) and also contain the coming out of the sealing bead at their lateral faces.
The results obtained by the use of such edges, however, are rather unsatisfactory.
The approach of one edge closer to the other, even if done with extreme precision, nevertheless determines a point of discontinuity wherein the molten material tends to wedge; the door/window thus obtained, therefore, more often than not inconveniently has a thin plastic rather sharp burr which, to be removed, must be taken off by means of the above-mentioned finishing operations.
Nor should the fact be overlooked that, depending on the manufacturer of the doors/windows, the external faces of the profiled elements may have very irregular shapes, formed by the alternation of different protuberances and recesses which, during the melting of the plastic, may be subject to completely different deformation phenomena.
The same stage of manufacture of the profiled elements (which occurs by molten plastic extrusion) inevitably involves deformations not predictable beforehand, so much so that the manufacturing tolerances for the plastic profiled elements are rather large (around 5 tenths of a millimeter).
To complicate things even more is the fact that such deformation phenomena are often affected by environmental and weather conditions in which the melting takes place.
Ultimately, then, the profiled elements having the same nominal size but which are extruded in different seasons and/or in regions of the world several kilometers distant and/or using different extrusion machines, can differ appreciably the one from the other.
For all the above-mentioned reasons, the approach of the mobile edges on the lateral faces of the profiled elements is hardly ever done with great precision, or at least not with enough precision to ensure a high quality result.